It is similar, but at least written it looks different enough. Plus in my accent
Colin is not very "
LIN", but more schwa vowel *insert upsidedown e* (computers and I rarely get along).
So I think
Colin and
Lynn are fine as siblings. In how they feel to me I think they are actually really nice together.
Though there's many names out there with Lyn/n or "
LIN" in them if it's an issue. eg: Linley,
Madelyn,
Gwendolyn,
Jocelyn,
Linsay /
Linsey /
Lindsay,
Katelyn,
Aislinn,
Belinda...
http://www.behindthename.com/php/search.php?nmd=n&terms=*lin*+*lyn*&submit=Go