Somebody: I have no doubt you're going to consider this a vulgar point, but here it is anyway: in nature there are two varieties of altruism - that which is done for kin members, for example in wolf packs or on a larger scale, in ant colonies and that which is done for non-kin members for reasons of reciprocity. One example of the latter type of altruism is the vampire bat. Bats will go out out and feed on blood and then come back to their colony in a cave and share their meal with another bat. Research has demonstrated that the bat shared with is more likely to subsequently return the favor. Because blood is an unpredictable food source for vampire bats, it pays for them to give to others as a form of insurance for lean times.
So, uncompensated work for family members is *not* going to be the model we're looking for when we're trying to build socialism. Helping kith and kin is as ancient as the first colonies of communal algae, and is not going to be of use for assisting those not genetically close to us. By contrast, altruism due to reciprocity is a better fit for a non-capitalist society. We're going to have to think of ways to encouraged that kind of "you scratch my back, I scratch yours" behavior. This will require more creative thinking than quoting chapter and verse from "The Critique of the Gotha Program".