This is the tricky one
You need to check the mechanism(metal strip on edge of door) which is on the edge of your first opening door. and slave door ( normally shut door ) They ideally would have metal bolts that shoot into upper and lower frame when in locked position.
If not fit Sashjammers x4 to top and bottom of each door. this is not a bad idea even if they have the bolts..
Depending how far you want/need to go you can upgrade the mechanism considerably but it costs a lot £100 upwards. You can have a mechanism that goes round all 4 edges of your door with locking points all the way round.
Are your hindges external???(open to attack) Can be upgraded again not cheap
Who made the doors??? (best have a metal frame internally(strong))
Do the frames have metal frames in??
Dont wanna scare you, but you asked
