Can I ask how you put them to bed?
DD (almost 5mo) will fall asleep in her cot for naps occasionally although often she ends up napping in her pushchair, bouncer or sling as I also have DS 2.5 and can’t leave him to take her upstairs and get her settled. At bedtime she feeds for hours and we end up going round in circles with feeding, putting her in the cot, her getting angry, getting her settled, sleeping for a bit, and then getting angry again, feeding again etc. Eventually she goes down properly at about 9/10 and does sleep through the night so it’s not a massive issue but I would love to have some kind of child free evening eventually! She does feed to sleep, and then I end up waking her a little bit as I put her down (deliberately) but I wonder if there is a way to do it without breastfeeding for hours on end!