spouse immigration

Hello everyone. I am new to this forum, I had a few questions regarding the immigration procedure.
My mother is a British citizen and lives in Kenya with my dad who is a Kenyan citizen, is there any way that he can be sponsored by my mother to become a British citizen or any way that both of them can move to the UK? They have been married for over 20 years.
Thank you for your assistance.

Start here - he can apply to have leave to remain in the UK if she is returning to the UK with him: https://www.gov.uk/remain-in-uk-family/overview

Note the English language requirements and the financial requirements.

After 5 years on a settlement path, he'll be eligible for Indefinite Leave and then (providing the rules don't change) he'll be immediately eligible for british citizenship.

He may also be eligible for an ancestry visa if he has any british citizenship in his history (although gathering the evidence can be tough!) https://www.gov.uk/ancestry-visa/overview

Thanks you for your response, I will look into it and post if any further questions. thank you