Certainly it is reasonable to expect to be sleep deprived as you adjust to starting a family (or adding to your family).
But it's not reasonable to live with chronic sleep deprivation, to accept that you may never sleep well again, or to literally endanger yourself and/or your children--even perfect strangers--with the side effects of sleep deprivation, which are serious and have major consequences, like drowsy driving, poor job performance, and even behavioral disorders which could actually put your children at risk for abuse or neglect.
Even in the long-term, trying to shoulder your way through life sleep-deprived not only doesn't make for healthy living, but it is a negative behavior that you could be handing off to your own children by default example. Sleep deprivation can also lead to disastrous marital consequences if left untreated, as well as long-term medical consequences. You want to see your grandchildren born, right?
It is not a badge of courage, competency or superhuman excellence to go through life sleep deprived, especially if you are a parent. If you suffer from a hefty sleep debt, please consult your healthcare provider about ways to get your sleep schedule back on track. Sleep is the critical THIRD pillar of help, equal to healthy diet and regular exercise. It is not optional. Not even for new parents.
Want to learn more? The Science of Mom blog covers "Sleep Deprivation: The Dark Side of Parenting" quite comprehensively.