[name]Natalie[/name] and [name]Nathan[/name]???
Too close/matchy for a sibset?
In a word, yes. Sorry! I just think that [name]Nat[/name] being a potential nn for both of them is too matchy.
I don’t think they are too close. [name]Even[/name] though both names begin with “[name]Nat[/name]”, the sounds are different. Unless you are going to use the nicknames [name]Nat[/name] and [name]Nate[/name], it should be just fine!
Maybe you could use nicknames like [name]Alie[/name] and [name]Nate[/name] or [name]Nat[/name] and [name]Thane[/name].
haha well I know someone who has a 6 year old named [name]Nathan[/name], a 3 year old named [name]Abigail[/name], and 6 month old twins named [name]Natalie[/name] and [name]Lily[/name]. I think they had trouble agreeing on names and [name]Natalie[/name] was one they agreed on, so they chose it. But they went a little over board when they chose to name the twin that looks identical to [name]Nathan[/name] [name]Natalie[/name]. Anyway, I don’t really think they are too close in pronunciation since one pronounces the H, but spelling wise, they are way too similar.
I also think they are too close. [name]Nat[/name] or [name]Natty[/name] is a nn from [name]Natalie[/name], plus they both start with [name]Nat[/name]-.
What about other N names for girls -
[name]Noelle[/name]
[name]Nicola[/name]
[name]Nola[/name]
[name]Nora[/name]
[name]Naomi[/name] - I love this name. I think [name]Nathan[/name] and [name]Naomi[/name] would be cute together.
I also think they’re too close…
As and alternative, I don’t know if you want another N name, in which case I would suggest the same names as [name]Lisa[/name] above me ^^
If not, I’d like to mention [name]Michelle[/name]… I don’t know why, but I always link [name]Natalie[/name], [name]Michelle[/name] and [name]Nicole[/name] together, and maybe if you like one, the others won’t be too far of a stretch as an alternative… 
What if you did [name]Natalia[/name] instead?
There’s also
[name]Natasha[/name] or [name]Nakita[/name]
Yes, I find them too similar. [name]Anastasia[/name] came to mind instead of [name]Natalie[/name].
Is this for twins, or do you already have one child and are trying to names the second? If it’s the latter, then which is your first child? It would help to know so we can give suggestions!