If you have identified that your near and dear one has a trouble in understanding your conversation, or ask for repetition, or listens to music/television at a louder volume when compared to others. Then get his/her hearing test done.
Having a hearing loss doesn't just effects the person who has it . It also effects the others who are along with him daily like family members, friends and spouse
Convincing them may not be that easy.
But you can tell them that it is important for them before they loose the potential of hearing completely
Remind them that they need to get evaluated
You can also schedule their appointment and come along with them to give a positive support