How old were Mary and Joseph when Jesus was born?

Most sources claim Joseph was in his 90’s and Mother Mary was between 12 and 14. But, Scripture tells us, from what I’ve read and researched, God holds those 20 and over accountable for their actions/choices.

Numbers 14:28-30 New American Bible (Revised Edition) (NABRE)

  1. Tell them: "By my life”—oracle of theLord—“I will do to you just what I have heard you say. 29. Here in the wildernessyour dead bodies shall fall. Of all your men of twenty years or more, enrolled in your registration, who grumbled against me, 30. not one of you shall enter the land where I solemnly swore to settle you, except Caleb, son of Jephunneh, and Joshua, son of Nun.

Would God give Mother Mary a choice? If she was younger than 20 does that mean God went against his own principles? Was marriage of children allowed if this was the case?

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How old was Mary when she gave birth to Jesus?

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