keep someone in something—provide a person with smth. such as food, etc.:
- The uniforms were goofy, but the food was free and the money kept me in clothes and rock music.
keep someone to something—
1. cause a person to talk about smth. without letting his attention wander:
- Your patient may require guidance to keep him to the subject in hand.
2. make a person do what has been agreed:
- He wished to relinquish his last year at Harvard, and Cynthia had to summon all her forces to keep him to his promise of staying.