Hi Imashish...I read your post a while ago and just-now read through this entire thread...First of all, I want to tell you how sorry I am that you lost your little boy and that you and your family have been going through such grief. As others have already said to you, it's very normal and necessary that you, your wife, and your little girl all grieve and mourn the loss of your little boy, and yes, only time is going to lessen the intensity of the pain you all are feeling. It's still only been 3 months since you lost your little boy, and though I myself am 38 and have no human-children (I too, like your wife, cannot have natural-children due to cancer and surgery to remove my reproductive organs), I do however have children of my own, like you and your wife, they are my birds and my dog. Any time a parent loses a child, especially when it is totally unexpected and sudden, it's the greatest loss they will ever go through, and the most pain they will ever feel throughout their entire lives.
As I said, time will lessen the intensity of the pain you are feeling now, but your pain is not ever going to go away, as you lost a child who you loved more than life itself. And that's completely normal, to feel that loss for the rest of your life is normal, and it's perfectly alright and actually very healthy to cry about it, to talk about it with your friends, family, colleagues, etc., and to write about it online to other people who not only have lost a child or loved-one of their own, but who also totally understand the depth of your relationship with your little boy. However, once again, the pain of losing him isn't ever going to completely leave you, but it will lessen with time, and this also goes for your wife and your little girl. And a relationship that close and that meaningful in your life is not meant to go away, that feeling of loss cannot go away when you lose someone that you loved that much and was such a large part of your life.
What will happen with time, in addition to the intensity and impact of the pain you're feeling right now lessening, is that you'll learn to live with that pain, and instead of actually feeling that gut-wrenching emptiness that you're feeling now whenever you think about your little boy, eventually you will actually feel nothing but happiness and love whenever you think about him. That's what happens when we finally learn to live with our grief and realize that nothing we do is ever going to bring our loved-one back, but that we are blessed to have the many memories that we have of our lost loved-one, and eventually we'll again enjoy thinking about our lost loved-one.
The fact that you had such a close, strong, loving relationship with your little boy is such a blessing and a miracle, and believe it or not, many people who live in this world never have such a relationship with anyone, and they never get the chance to feel that kind of love for someone, or to get that kind of love in-return from someone. And even though this blessing of a such a strong bond and love was cut-short, far too short, the fact that it happened to you and your wife is very special, in and of itself. There are many people in this world that would be very jealous of your relationship with your little boy, even though his life was ended much too early, they would still wish to feel only a small fraction of the love you had with him, if only for one day...
The fact of the matter is that you cannot ever bring your little boy back, nor can you recreate the relationship that you had with him ever again. And most people who try to recreate a relationship that they had with someone who they lost too soon end-up actually feeling worse and creating nothing but more pain, and most importantly, more disappointment. Something that special is not meant to be easy to come by, and that's exactly what makes it special. It's to be cherished and fondly remembered, but never recreated...
That being said, what you can do is to make an entirely new relationship, a new bond, and have a new love with another bird that you bring into your life, and the lives of your wife and little girl. However, it's extremely important to remember that if you do bring home another bird to be a part of your family, that you are starting an entirely new relationship with this bird, it's not going to be Mithu, nor is it going to feel the same as it did with Mithu. It's going to be an entirely new relationship, a new bond, and friendship, and a new love with a new bird. And yes, you can love a new bird every bit as much as you loved Mithu...but it still won't be the same as it was with Mithu. There is nothing, there is no one who can replace Mithu or the relationship you and your wife or your little girl had with him. I fear that right now this is your goal, to actually find another Mithu, for a lack of a better way of saying it...and I fear for you because if that's the case it will no-doubt end in disappointment and heartbreak, both for you and for the new bird.
If I were you, I would not actually bring home another bird to your family until you are completely and totally able to admit to yourself, as well as feeling fine with the idea that Mithu is gone, and that any new bird that you bring home to make a member of your family is going to be just that, a new bird with a new name, a new personality, a new attitude, a new voice, and a new love. And once you and your wife are completely ready to start-over fresh by adding a completely new bird to your family, then and only then will you be able to create a new bond and a new love with another bird that is just as special as the one that you had with Mithu...
And whatever bird you eventually bring home and welcome into your family is going to be one extremely lucky bird, as I don't think anyone could seemingly love and care for a bird in the way that you and your family have...