Hello Xander, welcome to the community. hopefully i can answer most of these questions.
you character will start of in a family, you will not own your families land but if you do work for your npc family then you may be granted it through their will. you can buy land via exposition points or if you are a mayor your friends can buy villager tokens to grant you land for the settlement.
souls are your characters life force, they do not give skill bonuses really, but after your character dies it will retain some memory of past lives, giving your next character that you pass the soul onto via the "spark of life" quicker experience gain in the skills you used in past lives. this adds progression to your soul.
your friends can use your children for their heirs to join your family, so in the first generation i believe the only way of joining together in a family will be through marriage. i could be wrong about this though.
i also don't believe that you can gift your extra sparks, but in the merchandise store there is a "wagon for 2" this comes with an extra copy of the game you can gift to a friend and also a wagon for you to ride around in together.
hope this helped. cheers,