To be honest how you feel or respond to matters isn't really important in the sense that it won't make a difference - if your son is bi then he's bi. Though you can make that harder or eaiser for him to come to terms with. The thing about homosexuality is that it really isnt a big deal - they dont lead magically different lives or require special understanding, they just want their orientation to be considered as normal as anyone elses - which it is. Bisexuality isn't really about gender it's about being attracted to people - not every person - but people whose characters seem special and appealing. All that said, your son is still young and may just be trying to figure out who he is, he may eventually decide he's straight or he may become sure that he isn't - there's no time frame on it and not everyone knows from a young age, for some it can take years to really understand themselves in that respect. Some are never 100% sure but eventually learn to live with that. There's a lot of pressure to be different these days and to quantify any such attributes and label them but sexuality is a difficult pretense to uphold. Fundamentally though it doesn't change him and as for the sleepovers I see no problem whatsoever in him having male friends round as they're just that - friends. He wont feel anymore attraction to them then he does at school. So for now, allow him the innocence of childhood but respect that he's still growing up. If he's doing well at school and is staying out of trouble that's great - the rest can be worked out in time.