Can I cage 1 male and 2 female cockatiels together?

I have two female cockatiels, one a year and the other 9 months. I’ve always wanted to get a male cockatiel because of their adorable whistling and chirping. I also love their little heart wings and dances.

I have a very large cage suitable for 3. There are no hideaway huts, nest boxes, or tents.

I know that babies are always a possibility when you cage opposite sexes together. But if I introduce a male, will the females start being aggressive towards one another?

What can I expect?

I wouldn't. My male cockatiel, Fang, once fell head over heels in love with my then female cockatiel, Twinkle. When Fang reached maturity he would switch from his usually sweet, even timid self to being EXTREMELY possessive to the point of out-of-his-mind aggression towards Twinkle in the blink of an eye, and would relentlessly chase her around the house trying to mate with her. She would fall exhausted to the floor where I would intervene between them to protect her, and Fang would then attack me for getting in the way! Fang and Twink always had separate cages, and I would have to put Twink in her cage to keep Fang away from her and give her safety and some peace. They had no access to anything resembling a nesting site but Fang still took the tiniest "come-hither" look from Twink as an invitation to mate and with his level of aggression I cannot imagine what would have happened if I had, say been at work all day when Fang's hormones took hold and they had been caged up together!

Having babies only presents even further undesirable and potentially hazardous complications to their health. Others may have a different view on this but no, after that experience I would NEVER house male and female together.

I just wrote this for another member who was wanting a male eclectus--it's the same idea, only in your case, there is even greater potential for jealously and chick-killing (so that the male can breed again with the other female etc---your females may even start fighting):

eek..have you ever bred birds before? This is a complicated situation and I would definitely not get a 2nd bird, let alone a bird of the opposite gender. With a bird of the opposite gender:
1) You will put your bird's health at risk potentially due to egg-binding and prolapse possibilities. Plus- the new bird will have to be strictly quarantined (w/blood work etc) in a totally separate location for at least 1 month (that means not even wearing the same clothes when handling the birds initially).
2) your birds may or may not bond and if they do not, then they may fight seriously.
3) If they do bond then you will be less important to your bird. Your currently sweet bird could do a complete 180 if she takes to the new companion and that means pulling away from you.
4) If they bond their cage may become a location of aggression for "outsiders" e.g., you etc.
5) If they lay eggs then you either have to boil them and return them to the cage or let the chicks go to term, and if you do that there are BIG bills and complications involved....and often a lot of heat-ache (truth be told). Parents can kill their chicks, hand-feeding may become necessary and if that is the case, then you are looking at round-the clock feedings, a brooder, specific temperature and humidity concerns etc etc.
If they DO raise chicks, where will you house them? If kept in the same cage together, they will mate eventually or even fight. If they mate then you end up with an inbred mess (birds with genetic issues). Therefore, each chick would also needs its own cage.

Back to the original point---

6) if they do not get along and you already do not have enough time to keep your female happy, then what will you do? If you can't give one enough attention, how will you manage 2 on totally separate schedules?
You should never get a bird for your bird because they may not even get along. It could end up that you have to devote equal amounts of time to these birds in totally separate spheres----many cannot be let out at the same time. Even if they do appear to get along, you will always have to be vigilant. Many members on this very forum have lost birds (or bird body parts-eyes, toes etc) to other members within their flocks.

I am not saying this never works, but if you are bent on doing it, I would STRONGLY suggest a bird of the same gender.

Keep in mind, even a bird of the same gender can trigger egg-laying in your bird but at least the eggs wouldn't be fertile.

There are people who keep multiple birds of the same species, but unless your goal is to reproduce then there is no purpose to get birds of the opposite gender. The bottom line is getting any new bird (gender aside), this is a HUGE gamble that could actually make your bird LESS happy and cause more trouble for you (if you are already pinched for time when it comes to spending adequate hours with the one you have).
With birds of opposite genders, it is really a lose-lose situation for you unless your only goal is to get chicks and keep them as a breeding pair...without concern to their bond with you or your family.

3 parrots in one cage is the worst possible multiple combination (not considering different species). I did it with Bourkes and had to seperate one. At the begining everything was ok but after few weeks one female started more and more chase male and another female

I wouldn't either. I had a friend do this many years ago and it was an absolute disaster. I'm sure it doesn't always happen this way, but unless you are are really prepared for breeding, I just wouldn't risk it. Not only were her original birds not as friendly to her, but the babies were in bad shape and she didn't even realize it. I saw them and was horrified. I pulled them for hand feeding and got them to a vet but we still lost half of them and the vet bill wasn't cheap. She separated the male after that.