Yes!!
I would be more concerned with how people would pronounce with that spelling. Killian is fine!
@Linda my son is three years old and it’s a traditional Irish name. I’m not worried about his name I’m pregnant with a girl and wondering if naming my daughter Collins would be too similar to my son’s name Cillian.
I still say go for it! They sound cute together!
Girl if you like it go for it! Me personally really love it and love how similar they are. Like I have a Maddox right now and if I have a girl her names gonna be Madelyn and people are telling me they are too much alike but I absolutely adore it and that's what I wanted anyways. 😁 Do it if your absolutely in love with it!! 🥰❤️