A surreal experience; My brother came out to my dad- and then vice versa

I really wanted to share this experience but felt the need to make a throwaway for it first, as a precaution. Also apologies for wall of text, TL;DR at the bottom.My older brother (28) and I (M23) were raised by our widower dad. When my brother was in highschool, there were some rumours about him that I heard, and I had see how close he was with one particular friend of his. Over time it became an open secret between us that he was gay, we must have verbally confirmed it at some point I don't remember. Anyway I never held it against him, but because of him whenever the topic of gay rights n that came up I always felt very empathetic about it. After school I considered myself an ally, made a few gay, lesbian, bi friends through my brother, etc.. But there was always the looming question of him coming out to dad.Dad's a sort of old fashioned bloke, somewhat religious, doesn't like fads or change (and would express a kind of resigned disgust when emo became a thing). He'd never expressed anything in particular that was homophobic, it was a topic that seemed avoided. The only time I can remember us talking in depth about it was dad talking about some 'poofs' (which he would say without a note spite) he knew in previous jobs: he liked the guys because they were hard working and loyal.My brother (Steve we'll call him) has a boyfriend now and they seem pretty serious, so Steve decided it was time to set the record... uh clear with dad and tell him and he wanted me to be there. More than happy to of course. So the big moment comes, we were round for lunch just the three of us, sometime after we'd finished eating but still talking Steve took a breath and said something like "Dad. I love you. There's something I want to tell you and I've wanted to say for ages. I'm gay." Dad looked down into the middle distance and said in classically, laconically, dad fashion "I hate to piss on your parade, Steve, but I knew that around about when you were 10." Steve was disarmed but relieved, I could see he stoically fought back tears. Dad even worked out who Steve's bf was. We had a great talk, Steve stayed a lot longer to hang out with dad than I did but it was a great moment.I did feel a small amount of resentment because I felt dad should have said something a long time ago but I'm sure he would have if he thought Steve was really hurting.That was last saturday and some things happened since then, like dad meeting the bf n that. Yesterday though we were around at dad's again, the 3 of us, having tea (dinner), and he says he has something to tell us. He said something like "Your dad's bisexual, boys. I honestly never thought I'd be saying that to yous, I didn't think it'd ever matter. Kids are the ones that come out to their dads, not the other way around" We were just... I mean, rattled. I had never picked up on this side of dad and am still kind of trying to harmonise it with my understanding of him. He also said that with all that's changed on LGBT stuff in recent years, and with Steve being gay, he felt he might as well share his secret. I asked "Is this your biggest secret?" He says with a laugh "No way, I have to save something for after I'm dead!" (Might seem a bit ominous to you but take my word for it that that's his blunt humour).He had a bunch of stories to tell us about the few guys he'd been involved with. We learnt even that him and mum got together after a guy had ran out leaving him with no where to go or stay. Him and mum were friends, she looked after him for awhile and they started dating a wee while after that. Mostly the stories were sad which is why I don't think he wanted to tell us till now. He said he felt like he had left all that behind when he got married.Later on Steve pointed out to me that I was the odd one out now. That was a sobering thought, I'm the straight guy in a gay-ish family! But it's cool, I love dad and my bro.Thanks for reading, r/ainbow! Love you fellas.TL;DR My brother came out to dad as gay a week ago, now dad has come out to us as bi. I'm the straight guy in the comedy troupe now.