This is a fascinating question, as Alcott was writing in a time when there were very strict and uncompromising societal ideas about gender roles and what it was to be a woman and a man. However, due to Mr. March's absence for a significant section of the novel, the reader is presented with Mrs. March, or Marmee, having to fulfill the role of both father and mother to her daughters. Alcott seems to be quietly challenging rigid notions of gender roles, suggesting that women are far more resourceful and able to fill the void left by absent males. When Mr. March does return, he remains a quiet character who is not fleshed out, mainly offering philosophical advice and promoting traditional notions of gender roles. Consider, for example, the following quote that Mr. March says to his daughter, Meg, about all of her hard work in the household:
I remember a time when this hand was white and smooth, and your first care was to keep it so. It was very pretty then, but to me it is much prettier now, for in this seeming blemishes I read a little history. A burnt offering has been made to vanity, this hardened palm has earned something better than blisters, and I'm sure the sewing done by these pricked fingers will last a long time, so much good will went into the stitches. Meg, my dear, I value the womanly skill which keeps home happy more than white hands or fashionable accomplishments. I'm proud to shake this good, industrious little hand, and hope I shall not soon be asked to give it away.
Mr. March is praising his daughter for all of her hard work in the house that keeps it looking so lovely. He is praising the "womanly skill" that maintains a stable home, but at the same time he is deliberately reinforcing gender stereotypes, saying that the home is the sphere and responsibility of the woman and nothing else. Note to at the end of this quote he deliberately alludes to the one future that women could look forward to: marriage. Fatherhood, as seen in the character of Mr. March, therefore seems to be more about reinforcing and promoting traditional ideas and beliefs about women and their role.
Alcott depicts the idea of fatherhood as being a caretaker to one's children and family. Mr. March is the father of the family, but in terms of the providing the experience of fatherhood, Mrs. March assumes the primary role being caretaker as well as mother and father to the girls. Marmee is as much a father to the girls in the narrative as Mr. March could be. While he is there through his letters and his thoughts, the reality is that Marmee is the father and mother to the girls. Marmee teaches the girls to be strong and independent as well as to follow their own path in being in the world. The message that comes from this is that fatherhood, and whatever it contains, can represent a form of caring and nurturing that can be provided by a mother. While there are gender specific roles in the relationship between Mr. and Mrs. March, his own inability to be there for the girls is something that Marmee is able to assume quite well and with a great deal of power. In this, Alcott is able to show that fatherhood and its tenets can be accomplished regardless of gender.