I suppose that for me, love and commitment isn't necessarily about sex.
My parents also were sexually monogamous for 50 years until Dad died this year. But I'd still probably call them both polyamorous - they were (are in Mum's case) an inspiration to me in their ability to form loving, committed relationships with other people.
I spent my childhood surrounded by their friends - many of whom I am still close to.
My parents loved widely and well. They just didn't have sex with anybody other than each other.
Didn't stop them experiencing many loves.