The sows can have three to four litters a year even.
The gestation period of swine is 114/115 days.
Wildlife people often take information pertaining to domestic swine and apply it to feral hogs, ignoring the fact that feral hogs have a hard scrabble life compared to their domestic cousins.
IME: In a year when acorns and pecans are plentiful or the hogs are dining at feeders, a few feral sows bear two litters. The litters average 6 or 7 pigs. Any lactating sow will suckle any pig in the sounder. While foraging little pigs are often left with a nurse sow/s.
When approaching a pond, feeder or game plot the sounder will often kick a juvenile up front as the point pig. i've often seen the point pig come running in with it's hackles raised, obviously scared.