DS was 21 months when DD was born, they are 5 and 3 now. We were fortunate that DS was a good sleeper. DD was not, at all, and if they'd both been poor sleepers it might well have broken me. We had a good bedtime routine with DS though and we did whatever we could to slot DD's bedtime into the same routine, once she started actually sleeping. We went into lockdown when DD was 4 months old as well, which added it's own set of challenges.
There have been good bits. We found that they used a lot of the same stuff, things like the bassinet, high chair, bottles, bibs, plastic plates, cups, changing table etc etc and clothes and toys too. We only had to babyproof everything once. We went through a phase with DS and then very quickly DD seemed to follow along, so we never really got rid of anything until DD was done with it. DD basically wants to do the same as her big brother all the time.
DS started potty training at 2 y 3 mo, while we were in lockdown seemed like a good time to do it. DD followed along at just turned 2, having seen her brother using the potty, and wanting to do the same. Likewise DS had a booster seat at the table rather than a high chair so DD wanted one too.
They play with all the same toys, and play together a lot. They bicker and fight sometimes, but on the whole they are each other's little companion, which is lovely. I worried that I couldn't possibly love a second child as much as I loved DS. But it turns out you really can. I wouldn't change what we have for the world now.
There have been bad bits though. At times it has felt like we're in the trenches a bit, having two small ones relying so much on us to do everything for them was exhausting and relentless at times. Going out with two children in nappies is a bit of a mission, I always seemed to have to take a tonne of stuff. Finding someone willing to babysit both of them at once was tricky, although it's got easier as they've got older. We invested a lot of money in two sets of really good 360 rotating car seats, because putting them both in and out of car seats, and switching the seats from one car to another was killing our backs. We spent a lot of time teaching DS to be gentle with DD when she was tiny, he was a chunky monkey and not aware of his own strength, and could eaily have hurt them. When it got to the stage that they were both walking, I had to watch them constantly, because they were capable of getting into mischeif in the blink of an eye. That phase was particularly relentless. And I have regularly felt pulled in different directions, when they have both needed me for something at the same time, particularly when DD was tiny and still breastfeeding, I had to be there for her, and I felt it so much when DS needed me and I couldn't be there right that second for him.
But as they've got older and become more capable themselves it's got a lot better. They are both independent little things, and they clearly adore each other. And the baby and toddler phase is done and dusted, never to be worried about again, thank god. (Although I do get broody when I see squishy little newborns).