"son Lilian" Wow. This is not a name I would ever think could go for both sexes. I guess in French it is not the feminine form, though? Is this in common usage in France for boys?
I'm not sure how popular Lilian is for boys in France, but I have heard of the footballer Lilian Thuram (full name Ruddy Lilian Thuram-Ulien) and Wikipedia has turned up a few other male Lilians, so apparently it's not that rare at all.