Boar milking glit?

Hello,

I have a brother and sister pair of Blackworth hogs and it appears that the boar is drinking the gilts milk from a nipple. Anyone have any experience with this? I was planning on raising them till she got pregnant then slaughter the boar. I saw some milk on the boars mouth so she is definitely lactating. Does this mean she's pregnant for sure? Any idea how far along? The breeder says they were born in June but he wasn't sure, they might be older...

Thanks!!