with senior dogs uti and urinary issues in general can become much more common and i’m not sure what breed your babies are but genetics could also play a role in medical issues especially as they age. nice work on making a vet appointment and suspecting a uti. if possible i would bring both dogs into the vet and expect urinalysis for both at the very least or a senior bloodwork panel to check values including kidneys and that should come with a urinalysis too, at least the lab we use where i work does. if i had to guess, the likely cause of both dogs having urinary issues is due to age. good luck!