Hi and welcome!
You may find that integrating a single piggy with a well established adult couple is often not quite sucessful. Trios are the trickiest constellation to get just right without ending with an outsider problem of some sort. The successful trios that I have had have all been together by their own choice (preferably by dating/meet&greet at a rescue); the unsuccessful one was a pair of (as it turned out) squabbling sisters I rehomed for a bereaved neutered boar of mine. Both girls got on well with the boar but not necessarily with each other.
If you can, rather consider dating your two ladies with a neutered boar, who by virtue of his gender is not quite part of the same hierarchy but needs to get on with both girls, or rehome two bonded young sows that will then have each other for comfort and company - four piggies constitute a mini-group with slightly different behaviour. This should neatly avoid the dreaded trio/outsider problem, which is entirely character based and therefore not necessarily predictable.
You can find bonding tips at the top of this section.
Could you please add your country, state or (for the UK) your county to your details, as your location will greatly inform any further advice on how to best go about finding a suitable addition and the option you have. Click on your username on the top bar, then go to personal details, then location. In the same section you can also upload your avatar. That is the picture that always appears with your name.
