What are the signs that a guy is bisexual?

I actually had a boyfriend and he broke up with me two months ago after being in a one year relationship. Mostly was LDR by the way because he works at sea. His reason was, "I feel so confused and I need to be alone. I need freedom" "it's not you,it's me" kind of thing.
We havent communicated since we broke up.
But the issue is, I saw some photos of him going on vacation a couple of times with his college best friend. I actually met his "best friend" once but I though he was "gay" because he had eyeliner, contact lenses and feminine ways. But I ignored that thinking that he was just a "feminine guy". But littlle did my ex-bf know that it kinda bothered me.
He went to a different city before working and his best friend also went there. My boyfriend was a little sick at that time and I was shocked to know that his best friend took care of him and they were in the same room. I ignored it again because I loved him.
But as time passed by, I have heard a lot about his best friend that he is indeed "gay". I was finally convinced that he is, because a common friend said that she knew who his lover boy was.
Then lately, after we broke up i saw posts from his best friend's page that they were together on trips. Not just the two of them, but with other gays too.
I know i shouldnt be bothered about this too much because we broke up already.
But i just wanna know, is it possible that i had a BISEXUAL EX-BOYFRIEND?
How can you tell/if a guy or your boyfriend is BISEXUAL?
I Just thought it would be a record for me or something. Because he was never feminine to me. Except that his sisters would tease him as being"girly". And had girly posts on facebook (both pictures and statuses) which I ignored back then.

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