Not so much weird as it shows that you are a very affectionate person. However many people will find this weird/not understand because this is more commonly seen as something two partners will do not family. I know most people will cheek kiss though if that helps =)
personally, I don't think so. I used to kiss my cousins on the lips - male twins. They were always extremely affectionate and did that with all the family members. I don't anymore, it just kind of faded out, but I understand and don't think it's weird :)
I find this quite strange and out of character, simply because I was not brought up around that form of affection with my siblings. Anything that a human does not see in their everyday life is always viewed as strange. So in respect it only matters what you think of it. Because some will think it strange, others wont.