We got DS guinea pigs when he was 13. He loved them and looked after them really well - they lived in an open pen in his room.
We realised at the time that they could outlive his interest in them and made a provisional plan - before buying - that they could go and live with his grandmother, who agreed.
3 years on, he has started A levels and has a busy social life. The guinea pigs now live in a hutch in the garden. They have not been out the hutch except when he cleans it and I frequently have to check they have hay. I checked them this morning and they had NO WATER in their bottle. This is the second time it has happened.
I have just talked to DS about it and he was uncommunicative but said he had forgotten them a bit and would try harder. I said this isn't good enough, and unless I see them getting some time out of the hutch and no more lapses in basic care, I will rehome them. There is also a family nearby who would like them. He will not consider these options and won't look me in the eye or discuss this properly.