Help - puppy kept in garage

My brother in law bought a puppy a few months ago after a breakup. He was very attentive with the puppy. Shortly after he got a new gf and the dog has been forgotten. It’s kept in the garage with the lights off in a playpen with a blanket covering the entire thing and a table on top to keep him from jumping out. He has some water in there but no food. The dog is fed once a day and let out for about an hour and then put back in the garage. It’s breaking my heart knowing this is going on. Everyone in the family has tried talking to him, to find another home for the puppy that’s now 5 months old. I even asked if I can take him temporarily until he finds a permanent home for him. He refuses to give up the dog and is now ignoring everyone’s calls. I don’t know how else to help. Hoping I can get some suggestions.