You ever got one of those family members that can not put the cap on the drinks properly?

It's usually the elderly who struggle, esp. if they have arthritis. Could also be a diabetic/neuropathy issue if they're not able to seal Ziploc bags (assuming it's a lack of sensation, rather than strength).

Yes, when my father was in his 90's he had trouble with that, as well as other small motor skills.

It will happen to most of us if we live long enough.