You can neuter your boys if you wish to - just as long as you do not expect them to get on better or be able to live together with a sow.
Please read the pregnancy information. A vet can realiably diagnose a pregnancy only in the last third (ca. 7 weeks) when the embryos are developed enough to show up clearly on a scan or x-ray; that is about the same time you should notice signs of a pregnancy. Before that, it is far to easy to mistake inner organs for embryos; we have seen that often enough! A first-time pregnancy lasts for around 10 weeks.
We have also included picture from scans and x-rays in our information pack. Our pregnancy and baby guides have been specifically written for owners with no experience and are very practical and step-by-step.
You are welcome to ask any questions you may have or that have come up while you have been reading the information pack. It has taken me days to write it; I can't repeat it all for everybody all the time, please respect that.
You are facing a rather steep learning curve; take the time to work through all the information. Concentrate firstly on your piggies' health before you start planning for the medium or longer future.
Your sow can live with any daughters of hers, a new introduced sow or one neutered boar. The best place to find a new mate of her choosing would be a good standard rescue where you can be sure that you you only adopt any healthy/fully quarantined/vet treated piggies that are properly sexed and guaranteed not pregnant and whose personalities are also taken into account. Mutual liking and character compatibility are the key to any successful piggy bond. Shops and breeders just can provide that; a good rescue you get a lot more service for total peace of mind and avoid neatly all the problems that await the unwary. Please be aware that anybody can call themselves a rescue in English speaking countries without licensing and control, and the results can be accordingly. here are links to rescues in several countries that we can guarantee for:
Recommended good standard rescues UK:
Recommended Guinea Pig Rescues
Guinea Lynx :: Rescue Organizations
Please keep your existing boar pair as it is; for the sake of their wellbeing. When it comes to boars, the rule is that two boars are best and that you do not break what is not broken because they are most fragile of all piggy bonds.