I prefer Cailin, though I've seen this name spelled so many ways and they all look fine. Either way is good, IMO Some middle name ideas:
Cailin Jennifer
Cailin Penelope
Cailin Judith
Cailin Yolanda
Cailin Mae
Cailin Brooke
I am not usually a fan of the y, but in this case, I think I prefer it. As PP noted, Cailin is easily read as Caitlin (or even Collin), particularly because all of those letters in the middle are basically the same shape. I am a Caitlin, and I can attest that that combo of letters is often misread because they do blend together.
I actually wanted to use this name for many years. I have changed my mind over the last few years, but my intention was to spell it either: Kaelin or Kaylin.
Re: Cailin or Cailyn?
Lost Lilah (Audra's twin) at 26 weeks. Cause unknown. Forever in our hearts
Cailyn, though I am not a fan of this name
This exactly... Sounds like you are trying way too hard to make a classic name trendy.
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BFP #2: 8.31.16 Dx w/ GD @ 28w DD Born @ 36w: 4.21.17