Thoughts on being a married single parent

No, not a typo. I have been married for 4 years now with a 3 year old daughter and a 15 month old boy. Yet I find myself falling into the category of something like a single parent. Thankfully I do not have to work outside the home so I get to raise my children full time. And I can't imagine how real single parents actually make that work. It's just that when my "partner" is here, I am still doing it full time. My kids get bedtime hugs and some play time but that is about it. Occasionally a diaper gets changed and the toddler taken to the potty but the parenting is really limited. Limited by being a visionary and self-employed but a workaholic at that and then by baseball with his son who almost lives with us full time. That is another story. I am sad for my kids who don't get a lot of his attention, who don't get the balance of being raised by another person besides me, by rarely being refreshed so that I can do it all again tomorrow or an hour from now, for that matter. Don't get me wrong, I LOVE my kids and know how lucky I am that I get to spend so much time with them. Time does go by so quickly.... heavens my daughter is already three. (How did that happen?) But it is good for them to have one on one time with their dad. He is a good person and has a lot of love to give them. I understand that he is tired at the end of the day (uh, me too), running from this end of the earth to the other end of the world each and every day but that doesn't change the fact that his little kids need him and want his attention. He isn't usually working when he comes home when I feel that he should spend time with the little ones in the hour that they are still up before they go to bed. I have even postponed dinnerhour and thus bedtime so that they get to see something of him every evening. But he usually ends up in front of the tv or visiting with his older children. I am not trying to get my kids to "compete" with the older ones, it's just that they are going to be awake longer than the younger ones.
Sometimes, I need a break. Anyone with young children knows that not every day is easy. Whether it goes well or not you still have to try to paste a smile on your face, good thoughts in your head, and cheer in your voice as you keep slogging on. But in my household it doesn't matter. Even if I have had the worst day ever, I am still the one who gets them ready for bed, teeth brushed, jammies on, stories read and tucked in until they are asleep. My husband has never done it. Never spent more than 2 hours alone with them ever. Not even when I was sick with the flu and throwing up. (Thank GOD for girlfriends - and that is another story!) He hasn't cut a single fingernail. He doesn't know where I keep the underpants if the toddler has an accident. (Never mind they are in the top drawer of the dresser which she can't reach, I mean not everything fits in the bottom three drawers, if you know what I mean.) What is the deal? I wonder if it is because we are married that he feels they are taken care of and thus do not need any help from him. I hope that my children grow up healthy and happy and think good thoughts when they look back on their childhood.