My brother and I are in our 30s. He still lives at home with our mum. I've moved out (thank god!), but had to live with their odd relationship and routine for many years, and according to them, it's still ongoing.
He's always competed with me for her favour, ever since we were kids. But it got worse when our parents separated, it's almost like he's took on the role of being her surrogate husband?
They set their alarm clocks to wake up at the same time as eachother, if one of them has to get up earlier for work, the other one will set their alarm accordingly. They spend hours talking every morning, drive off to work together, drive back home together and then spend 1-2 more hours talking about their day. They don't go anywhere without eachother. They go shopping together, they visit people together. Etc etc.
He agrees with everything she says, hangs onto her every word, she's never in the wrong in his eyes, they slag people off all the time (including me!) and egg eachother on. It's bizarre. I feel awful anxiety speaking to them now because I know when I walk away they're gonna be slagging me off, as always.
Any kind of argument I had with her as a teenager (just normal arguments teenage girls have with their mums), he'd aggressively square up to me, shouting in my face, calling me every name under the sun. She'd then thank him for 'standing up for her', then come and ask me if I was okay and tell me he was out of order ??? 
I felt suffocated and stifled in my own home for years.
Now I'm not allowed to have any kind of disagreement with her without him involving himself and getting aggressive with me.
I'm not being nosey, it wouldn't bother me at all if it wasn't for the fact that I'm not allowed to have a normal relationship with my own mother. I can't speak to her on her own, she's always with him. He makes it a them vs me situation all the time, and gets confrontational and competitive with me. I have to walk on eggshells and watch what I say.
I lived with them and their behaviour for so long and whenever I tried to bring it up they made out that I was the weird one. But surely it's not just me that thinks this is completely fucking abnormal?