the sims

i got my little bro the sims for christmas, its the first one for ps2, he created his family which was just a man and a woman. how do they have kids, he got the special heart shaped bed and hot tub, but they
sometimes will do thier thing in the bed but he cant get them to do anything in the hot tub. whats wrong with them?

i dont play the one on ps2, but on pc you just have to make them like eachother.