For my story I have twins with both their names starting with the same letter.
[name]Orion[/name] and [name]Ophelia[/name]. Is that tacky? I just really like how well they fit together, at least for me. I was thinking of [name]Ry[/name] as a nickname for [name]Orion[/name] and [name]Lia[/name] as a nickname for [name]Ophelia[/name]. I’m stuck on their last names…
The story is action/adventure. They’re the best friends of the main character, [name]Sophia[/name].
I feel like [name]Orion[/name] and [name]Ophelia[/name] are too matchy due to the O. They sound great together, and have similar feels, but the O thing makes it all feel like too much.
I could deal with it if you used [name]Rio[/name] as a nickname for [name]Orion[/name].
I think it’s fine that their names start with the same letter, because while it may seem a bit tacky, parents [name]DO[/name] give their twins rhyming names sometimes. However, I think [name]Sophia[/name] and [name]Ophelia[/name] sound too much alike.
Also, ‘[name]Lia[/name]’ seems like a weird nickname for [name]Ophelia[/name] because nicknames tend to either be based on the emphasized syllable or first syllable, but also because “[name]Ophelia[/name]” tends to be pronounced “o-[name]FEEL[/name]-ya” instead of “o-[name]FEE[/name]-lee-a.” [name]Lia[/name] just doesn’t seem like a natural nickname of [name]Ophelia[/name].
I don’t think this is tacky; in fact, you’re being realistic with the pattern of giving sibilings the same initials. I do think these names are a bit outdated, though. And be careful when considering names of already well-known characters; in my mind, as well as any others, I’m sure, [name]Orion[/name] will always be the character from Greek mythology, and Ophlia forever linked with [name]Shakespeare[/name].
It’s NOT tacky; it’s awesome! I totally love the nickname [name]Lia[/name] for [name]Ophelia[/name]!
I think its fine that they start with the same letter because seeing the name of the main character, they’re names kinda of flow together as a group and I like the idea of [name]Lia[/name] as a nickname for [name]Ophelia[/name] 
I think it’s OK because their nicknames start with different letters.
I think that they sound fine together! But I wouldn’t do too many nicknames… I feel like one twin should go by their full name and the other by a nickname, otherwise it is too much for the reader to remember. SO, maybe [name]Ry[/name] and [name]Ophelia[/name], or [name]Lia[/name] and [name]Orion[/name]. Anyway, just a though. I also agree with above, though, that [name]Ophelia[/name] and [name]Sophia[/name] are too close. Maybe do [name]Sophie[/name] instead?