Hello, everyone! 
I wanted to wait a bit before replying because I wanted to give people some time to come across and reply to this thread. 
Anyway, I’ve through all the replies that y’all have given and there are SO MANY GREAT EXAMPLES! 
@lucy_halo1 [name_f]Caroline[/name_f] and [name_m]Charles[/name_m] don’t really seem alike, I agree. You could add [name_f]Charlotte[/name_f] and [name_m]Carl[/name_m] to the list, too!
@Poffin Yes! I’ve known that [name_f]Isabel[/name_f] and [name_f]Elizabeth[/name_f] are variations of the same name, but they are so visually different, that people don’t even realize they’re actually the same.
@EagleEyes I had no idea that Étienne and [name_m]Stephan[/name_m] were the same! 
[name_m]Louis[/name_m] and [name_m]Ludwig[/name_m] definitely seem more believable as being the same (since I find myself researching names all the time, I did actually know about these 2 already). [name_f]Alice[/name_f] and [name_f]Adelaide[/name_f] don’t really look alike, but I can definitely see the progression once it’s explained in the way you did. I knew about [name_m]Pierre[/name_m] being a form of [name_m]Peter[/name_m], it had never even occurred to me about Boutros (although, to be fair, I’ve probably only ever even heard the name Boutros mentioned once or twice in my life). I had actually known of the correlation between [name_f]Theophania[/name_f] and [name_f]Tiffany[/name_f] (as I’ve done quite a bit of research into the name [name_f]Tiffany[/name_f] because it’s my mom’s name). I totally agree with you on [name_f]Bernice[/name_f] and Veronica; they do not look alike AT ALL.
@justagirlwholovesnam It does seem like [name_f]Theophania[/name_f] is more medieval-esque than [name_f]Tiffany[/name_f]. I think both [name_f]Margaret[/name_f] and [name_m]Pearl[/name_m] are so great. And I think, given that the name [name_f]Margaret[/name_f] means “pearl”, it gives better context to why [name_m]Pearl[/name_m] is often a nn for [name_f]Margaret[/name_f].
@shanade21 I love the way [name_m]Iago[/name_m] sounds! In my opinion, I think [name_m]Iago[/name_m] and [name_m]Jacob[/name_m] sound more alike than looking similar to one another. [name_m]Theodore[/name_m] and [name_f]Dorothy[/name_f] definitely have a similar feel both visually and sound-wise. [name_f]Nancy[/name_f] and [name_f]Agnes[/name_f] look and sound totally different! [name_f]Etheldreda[/name_f] and [name_f]Audrey[/name_f] also do not look or sound alike AT ALL. I’ve actually known that [name_f]Sarah[/name_f] and [name_f]Sadie[/name_f] and [name_f]Sally[/name_f] are all related. I believe [name_f]Sadie[/name_f] actually started out as a nickname for [name_f]Sarah[/name_f] before people just started using it on its own.
@diane921 I’ve loved [name_f]Elspeth[/name_f] for so long! I’ve also been Sophronia-curious for a bit now. I really like how both of these start and end with same letters [name_f]Elizabeth[/name_f] and [name_f]Sophia[/name_f] do. [name_f]Love[/name_f] [name_f]Anais[/name_f] (more specifically the [name_f]French[/name_f] Anaïs)! This is probably my favorite version of [name_f]Anna[/name_f] / [name_f]Anne[/name_f] in any language [name_f]Amelie[/name_f] (or Amélie) and [name_f]Amelia[/name_f] are both lovely, too. You could add [name_f]Guinevere[/name_f] to go along with [name_f]Ginevra[/name_f] and [name_f]Jennifer[/name_f] (which is my aunt’s name; I’ve always just called her Jenna). [name_m]Saar[/name_m] looks really nice alongside [name_f]Sarah[/name_f]. Visually, these too look really similar (they’re both also Hebrew names), but their meanings are totally different (Saar means “storm” while [name_f]Sarah[/name_f] means “princess”). I really like [name_f]Giulia[/name_f] as the Italian variation for [name_f]Julia[/name_f] (I think maybe even slightly more than [name_f]Julia[/name_f] itself; although, I think I also might like it even more if you were to make it slightly more elaborate and turn it into Giuliana). [name_f]Sanna[/name_f] and [name_f]Susanna[/name_f] are both great, too. I Although, I think I like an “h” at the end – turning it into [name_f]Susannah[/name_f]. I’ve had a long-standing crush on [name_f]Emiliana[/name_f]! Dear sweet [name_f]Emily[/name_f] is okay, but I just adore her more elaborate sister. Whenever I see the name [name_f]Gretel[/name_f] I always think of “Hansel and Gretel”, but I definitely can see how it’s related to [name_f]Margaret[/name_f] (I’m certain I prefer Margaret). In my opinion, [name_f]Melisandre[/name_f] and [name_f]Millicent[/name_f] look more like cousins than sisters, but both are great! I actually have cousin (who’s actually a first cousin, once removed) who had a baby a couple years back whom she named [name_f]Millie[/name_f]. [name_f]Manon[/name_f] is such a cute diminutive of [name_f]Marie[/name_f]! [name_f]Majken[/name_f] as a variation of [name_f]Mary[/name_f] is just magical. Scandinavian countries always have such dreamy names.
@Nessie4 [name_f]Mary[/name_f] and [name_f]Polly[/name_f] look absolutely nothing alike, so that’s crazy that they’re variations of the same name! [name_m]Sean[/name_m] and [name_m]John[/name_m] and [name_m]Evan[/name_m] are more believable as being related (probably more-so [name_m]Sean[/name_m] and John). I’ve actually read about [name_f]Teresa[/name_f] and [name_f]Tracy[/name_f] being related! You could add [name_f]Tessa[/name_f] to the list, too.
@KaiLun [name_m]John[/name_m] - [name_m]Ivan[/name_m] / [name_f]Ivanka[/name_f] / [name_f]Ivana[/name_f] / [name_f]Jean[/name_f] / [name_f]Jane[/name_f] / [name_f]Jeanette[/name_f] / [name_f]Joan[/name_f] in this order looks like a fairly good progression of the same name. Btw, [name_m]Zane[/name_m] being a variation of [name_m]John[/name_m] is definitely surprising.
@Greyblue I think [name_f]Guinevere[/name_f] may be one of my favorite names ever! I love medieval and Arthurian it is. [name_f]Jennifer[/name_f] and [name_f]Ginevra[/name_f] are both great, too! [name_f]Jennifer[/name_f] is actually my aunt’s name (although, I’ve always just called her Jenna). I don’t think I’ve heard of [name_m]Tavish[/name_m] before. Which is a little strange because [name_m]Thomas[/name_m] is one of my favorite classic names.
@danilib [name_m]Iago[/name_m] – [name_m]Jacob[/name_m] – [name_m]James[/name_m] seems like a good progression. [name_m]Seamus[/name_m] looks like the outsider, to me.