MOTHER PLAY casting question

MasterThespian 2 said: "I’m a bit confused (not a rare occurrence). The synopsis on Mother Play mentions a mother overseeingthe move of her two teenage children into an apartment.” But those teens are being played by Jim Parsons andCelia Keenan-Bolger, who are 50 and 46 respectively. So, are they actually portraying teenagers? Are they reflecting back on events that occurred many years ago? Or something else?"

Keep in mind the play was written by Paula Vogel, who used adult actors to play characters from a large variety of ages.