I think for Ste it's a bit of a father figure thing, obviously. For Brendan, he chose young men for his regular relationships (Vinnie, Macca, Ste) probably because they were impressionable and manipulable and easier to mould and control, although he's got more eclectic tastes in his one-nighters. He just happened to fall in love with Ste
and I'm sure part of it for Brendan is the way Ste looks up to him and learns from him, and the way Brendan can look after him and cherish him. One of Brendan's contradictions is that he's a rubbish parent but is also instinctively strongly paternal. I'm sure it's a way of compensating for his own abusive behaviour, and also a reaction against Seamus's grotesque inversion of what a father should be.
Brendan wouldn't think of his relationship with Ste as father/son, any more than he'd think of his feelings for Cheryl as father/daughter, but his protective side is a paternal thing, and it's lovely.
