My 5 month-old kitten jumps on and attacks our older 7-year-old cat, who now is less friendly towards us.?

Our 5-month-old cat, who was a stray, jumps on and 'attacks' our older 7-year-old cat. We don't know if the kitten just wants to play or not, but the older cat doesn't like it. He is normally very friendly and loving, but he is indifferent to us now. The kitten bites us and the older cat, either as play or just being mean, or teething. We've had him for about 4 months, and he hasn't changed his behavior much. We spray him with water, put him in time out, etc. when he misbehaves, but nothing seems to help. What can we do to get him to stop biting, and what can we do to help our older cat to be normal again? Thanks.