keep in touch with someone—be in regular communication with smb.:
- An undergraduate is assigned to a “moral tutor” who undertakes to keep in touch with him.
keep in with someone —(coll.) remain on good terms with smb. (usually to gain some advantage from the person):
- We’ll have to keep in with her in case we can’t ever pay the rent.
Note: The expression does not correlate in meaning with the phrase keep up with someone—remain level with a person in some respect:
- You’re free to work at a pace that suits you, which means not having to keep up with others.