I think it's great, I thought of
Julian of Norwich right away. I don't mind it as a feminine name at all, but I like it as a male name too (although I definitely prefer
Julius).
For a brother and sister I might continue the Mediaeval gender-bending theme:
Wilmot (sister)
Jocelyn (brother)
Some combo ideas:
Julian WillowJulian EverildJulian RosalindJulian LeticiaJulian Mirabel
Your
Julian Wisteria is very lovely; I loved seeing all the wisteria when I lived in Norwich, and to me
Julian is a pale purple colour, so that's very appropriate! :)