Boar getting possessive over sow

[SvalbardianPenguin]

We have two Guinea pigs who are house pigs, they are both friendly and are handled often. This last week, the boar has been getting very possessive over the sow, he's not done this before but now he rumbles when we touch her and is grooming her a lot more, she doesn't mind. They are both six.
Any ideas please?

If they've always been a couple and he's never done the rumbling grooming thing then do a thorough check of her ears,eyes,and fur/skin in case she has any wounds or minor infections he might be cleaning.
Piggies have milky fluid in their eyes that is produced when they wash (that adorable sitting on their haunches and rubbing their front legs behind their ears and over their eyes routine )
It might be that she can't reach herself so she's letting him do it?

Our boar washes one of the sows ears but he's always done it and she tolerates it. (It is sweet to watch though. )

He might just be coming over all Leslie Phillips ( Oh Ding Dong Matron) but give her a good check over just to be sure there's nothing lurking.

He's always groomed her a bit and has rumbled when he wants to have a, ahem, more intimate relationship with her. What is new is the rumbling when we touch her sometimes and the way he will start grooming her as soon as we put her back in after we've had her out for a fuss. Usually they both come out at the same time but sometimes he backs away and rumble at us so we leave him be then - it doesn't happen often because he's very sociable; it's linked to when a carrot or banana is available for him eat I think!

Forgot to say, she's just been to the vet for her MOT so we're sure nothing is lurking.