Sins Of The Mother:

After a night on patrol Peter is approached by a shaken and visibly upset Black Cat he attempts to console her when she breaks down and reveals to Peter that years ago when they were still together she became pregnant with his child. Feeling too inexperienced and irresponsible to be a mother (not to mention having parent issues of her own) she opts to have the child aborted while still in its early stages of development.

Unfortunately due to the child having Peter's superhuman metabolism the abortion pill wasn't a complete success and the child while not killed suffered from a birth defect that means her son has to live on life support. Not wanting the child to be hurt by her career as a thief or even her father's life as a hero Felicia gave the child to a carehome for severely sick children. She then reveals that everything she has been stealing has in fact been going to pay for the child's medical bills which are astronomical considering he needs around the clock care just to keep breathing and kept this from him all these years for the simple reason that she was ashamed of what she'd done, feared what Spider-man might do and even thought she was protecting the child from their own dangerous lives.

She has only come forward to tell him now as her efforts to keep their son out of their dangerous life style failed and after a heist she was hired to do went bad and the loot taken by someone else, the client who hired her believed she had taken the loot for herself and is sending assassins after her who unfortunately found out about her son and wounded him in an attempt on her and his lives. The boy lost a lot of blood and every blood transfusion has been rejected by his body due to his fathers inhuman characteristics. Thus she came to Peter in the hope the he is a match for the boys blood.

Peter of course reacts badly all of this and demands to be taken to see the boy. When they reach the new facility (as Felicia changed carehomes in hopes of throwing of the assassins briefly) it is revealed that the boy has be kidnapped by the assassins in an attempt to draw Felicia out of hiding. Basically the rest if the arc would consist of Spider-man tearing up the city in search of the child getting more and more desperate and more and more volatile as the child without the blood transfusion doesn't have long to live.