Melinda French Gates never expected to be a grandmother at such an early age

Writing in her new memoir 'The Next Day: Transitions, Change, and Moving Forward', she said: "During this season, I've seen my life change in ways I hoped for, ways I fought against, and ways I never could have imagined.

"At 58, much earlier in life than I expected, I became a grandmother."

Although it took her by surprise, Melinda has embraced how "wonderful" it is to be a grandparent as Jennifer has since given birth to her second granddaughter Mia - aged five months.

The businesswoman - who is also mother to son Rory, 25, and daughter Phoebe, 22, - told People: "Any time I get to spend with these two little girls is just a delight.

"I beam thinking about it, like, 'Oh, I'm going to get to be on the beach with those little girls.' And, all that requires, the little sun hat and everything else, (like) the splashing in the water, but it's delightful."

Melinda says the thing she adores most about being a grandparent is the fact that she gets the chance to hold babies once again.

She explained: "It's a delight to be able to hold and snuggle a baby again. Or in Leila's case, she loves to run around. She loves to jump on a trampoline when you can find one. She likes to be on a little play set.

"It's so fun to just kick off your shoes and run after her in the yard."

Melinda previously described how she had been through some "painful" changes since her marriage to Bill came to an end.

She said when announcing her memoir last year: "Over the last few years, I've experienced a lot of change - some of it exciting, some of it painful - so I've done a lot of thinking and learning about transitions. I decided to start writing this while I was still in the middle of this season of change, rather than safely on the other side.

"We've all had days that change our lives forever.

"This book is about what we do the next day, when one phase of our life has come to an end, but the next phase hasn't quite yet begun. I've learned that if you can find the courage to linger in that liminal space, it has a lot to teach you."