I have two desexed toy poodles (brother and sister) who are 3 years old. They are inside dogs (we have cold weather). They have a doggie door to our back courtyard through which they access the backyard to do their doggy business. When we are at home (day and evening) they use the doggie door and go out to the backyard to wee without any problem.
However, when we are asleep at night my female dog wees and/or poos in the courtyard and her brother (being a male) wees over the top of hers. If we are all out during the day our female either goes in our house or in the courtyard. She refuses to go to the back yard at those times. We show distaste when we find it but we haven't caught them actually doing it.
I am not sure how to approach the matter as I have double trouble to manage. They are just perfect in every other way but mopping up is exhausting.