How they first met: They met through being Champion. There’s an annual meeting of all the regional Champions, so they met at one of those. Diantha became Kalos Champion after Cynthia, though only barely became Sinnoh Champion, so during Diantha’s first yearly League Conference, Cynthia offered to help guide her new fellow Champion around. They were good friends ever since then, often keeping in touch and meeting up when they were in the other’s region.   
Where their first date was: They had their first date after Diana had been Champion for about two years. Diantha was visiting Sinnoh for a movie shoot when Cynthia dropped by and asked if she would like to go visit an exhibit at the local museum she had helped curate? Diantha caught the implications that Cynthia was asking her out and blushed as she agreed. As filming finished up for the day and Cynthia showed up to pick up Diantha, all the other cast and crew were gossiping about this potential blossoming romance. 
When they had their first kiss: They have their first kiss on the fifth date, when Diantha meets Cynthia at the airport in Kalos and Cynthia greets her with a quick smooch.
Who cooks: Both of them can cook fairly well, but both are often too busy to cook, so they tend to go to restaurants or have a personal chef. However, when they have the time, they like to cook a meal together.
Who proposed: Cynthia.
The dominant one: Cynthia.
Their favorite pastime together: They travel a lot, mostly between their respective houses (more like mansions) in Sinnoh and Kalos, but when they have the chance they love to travel to other regions and see the sights, enjoy new foods, meet new people, and just have some nice time to themselves without the stress of work (or the kids, though their daughters are all quite well behaved.) Cynthia’s house in Unova is a popular getaway destination.
Who kissed who first: Cynthia kissed Diantha. 
Who is the flirt: Cynthia, she’s very smooth and is fond of making her wife blush, even after years of being married.
Who is the romantic: Diantha, hands down. She’s got a real sense for romantic gestures and is always very thoughtful when she wants to treat her wife to something nice. Flower bouquets, romantic dinner dates, she’s done it all.
Who wakes up first: Cynthia tends to be the earlier riser, Diantha often oversleeping a bit if she’s not careful.
Who comforts who the most: Diantha tends to be the more emotional of the two, having more trouble handling stress as well, so Cynthia tends to comfort her more after a particularly trying day. Diantha always tends to worry about the kids more, if they’re doing alright or getting into trouble or are they safe, while Cynthia is much more ‘hands-off’ once the girls are all grown and off on their own journeys. So she tends to reassure Diantha about that a lot as well, often gently reminding her not to blow up the girls’ phones with texts asking if they’re ok.
The cuddler: Diantha.
The big spoon: Cynthia.