Tywin and Cersei loving people is straight out of the books, Tywin loved his wife, Cersei loves her children, it's not out of character to show them having nice moments with certain people. It's more interesting than Tywin just being a bastard and Cersei a raging, stupid bitch. The only true Lannister sociopath is Joffrey and the show is doing a great job portraying him.
And Deckerd, if you haven't seen the show, watch it now! It's not perfect (neither are the novels btw) but it's a great adaptation. Don't let a few people on a message board talking about stuff stop you from experiencing it, even if you don't like it, you should find out for yourself