We have a 5.5mth old gorgeous but quite demanding baby. I'm on mat leave and I admit I've never really got my head around what's fair in terms of household/childcare split, but I don't think my DH spends as much time with our DS as he could. DH disagrees. My reasoning isn't so much to give me a small break (though of course that's appreciated), but so that they spend time together and bond. DS is calmed much easier by me, for example, but I know the only way that will change is by DH doing it more often.
That's the background, so I accept I'm already a bit annoyed before even getting into my current bugbear. Every time DH has some time with DS, without fail he will find something else to do first. So it will be time to give an evening bottle, and he'll just go to the toilet. Or make a drink, or eat something. Or write an email or something, leaving DS waiting. Today, he had given DS most of his bottle (DS was slowing and starting to play with it), then he said "can you hold him for a minute". 5 minutes later I realised he had gone off to water all the house plants! WHY that couldn't have waited I have no idea. I ended up giving DS the rest of the bottle, which defeated the object of both me having a break and them having bonding feeding time. I was clearly annoyed and DH said "don't you dare be in a huff with me for watering the plants" 
I guess with the going to the toilet/making a drink I am being unreasonable to be resentful. I think it comes from me responding to a needy DS in the early days immediately, I wouldn't have had time to go to the toilet or make a drink. (Ha! I sound like a right martyr!!)
But it is driving me crazy that he's doing things that could reasonably wait until DS is in bed when he could be spending time with him. After work there is so little time before DS' bedtime, and so much time after it, is it really unreasonable of me to expect DH to prioritise his son before houseplants/emails/other crap? Writing it down it feels petty but it is really really annoying me. DS was much wanted, DH was the one who always wanted children, I was the one who took my time to decide. We then had fertility issues and he was a long time coming. I know DH loves him, I just don't think he practically prioritises him in the same way I do.
Has anyone had this issue? Any ideas how to reasonably get my point across (if I am not being unreasonable, of course)?