Why do gay men always more promiscuous than straight men?

I'm a straight guy but,i have gay cousin and as far as i know (cause,we're close relative),he always has a different partner every week! he never afraid of ,brave to exchanging -partner with his fella and i don't know if they practicing safe- but..well,basically, i'm just wondering if there is a true love in gay world.How come they are always being wild? don't they also wish to be engaged in matrimony? sorry,if you find it a bit offensive