That's assuming quite a bit about the OP and myself, so I'll speak for myself: I'm married with four children.

I love what I do and directly sought a partner that would fit with my life and a job that is flexible. I work from my home for a team that is located entirely in the United Kingdom (I'm in the US). I don't regularly do "80 hour weeks" -- it happens and it's almost always by choice -- but there are ways to work more than 40 hours and not have it affect your family.

First, I eliminated the commute by working from home. This allows me to start work the instant I wake up, which I do every morning. A while back, I followed something I'd read on HN about 'how to wake up at 5:00 AM'[0] and have been doing it for so long now that I get up around that time every morning without effort and find it hard to sleep in at all. But I enforce an average 7 hours of sleep/day over a 5-day period[1].

When I work and where I work is flexible, but I'm always working until my team goes home. I also work entirely from my laptop, in the living room, all day. That means I'm basically with my family nearly all of the time in the summer (my wife usually sits next to me the entire day). I can close the lid when circumstances warrant. After that, it's a mix of day and night working (usually both). During downtime (which would otherwise be wasted by being dedicated to watching TV), my laptop is on my lap. My wife has her phone in her hands. She's always been like this and I've always been like this. I got lucky in that my wife and I share a brain on these sorts of things.

When there aren't plans on the weekend, I'll work during the downtime.

My wife is a full time mother, as well, so she handles the cooking (which I hate doing, anyway), grocery shopping and household related things. We both participate in homework, teaching, and enjoying our children. There are times when work is long and difficult and she's understanding that she needs to hold things together when those rare moments occur--I'm the only source of income for our family of four.

[0] The short version of the technique is "force yourself to go to bed when you're tired (even if it's at 6:00 PM) and force yourself to wake up by 5:00 AM". The former is easy, the latter isn't but I added another technique: I did several dry runs the night before where I set my alarm 5 minutes in the future, laid myself down and jumped out of bed when it went off. For the first several days, I physically got up out of bed and ran to wake myself. Now I can grab my laptop off of my side-table and sit in bed feeling perfectly awake. I drink a reasonable amount of coffee, as well but no alcohol (I gave it up a while ago because my sleep was affected negatively when I drank and I didn't enjoy it much, anyway).

[1] I've never been one of those people who can handle little/no sleep. I need 7 hours a night or I start to feel miserable and get crabby with my family, so I aim for 7.5 hours/night and enforce an average 7 over 5 days. I have bursts of creativity most often at night and if I'm having a particularly good time with code, I allow myself to stay up until productivity is affected by exhaustion. To make up for it, I will go to bed early the next day or grab a nap in the afternoon. As far as the whole "there's no way to make up sleep", that's not been my personal experience. I am right back to normal after a 4-hour evening if I put in a 10-hour night and I'm able to do it if I force myself to bed a few hours early. Because of "0", I haven't been able to reliably sleep in, so that's my only option left.