I’m afraid you can’t split a cage of that size and still make it big enough on both sides. You will need to make it bigger to be able to accommodate all piggies appropriately.
The two sows and boar need a 2x5, and the single sow could really do with a 2x4 - although a 2x3 strictly speaking does meet size requirements for a single piggy, it would be better for her to be in a 2x4.
if you tell us the space you have to play with, we may be able to help with a configuration - ie can you make the cage wider than 2 grids? For example - if you could make a cage that was 3 grids by 7 grids in total, then you could split it into a 3x4 for the trio and a 3x3 for the single sow. Or make a 3x6, giving the trio a 3x4 and the single sow a 2x3.