House - A house usually always represents you, or rather 'the self'...your body and the attributes of your personality. They symbolize our emotional and psychological selves. All of your experiences, stages of development, and parts of your conscious and unconscious life may be represented by that house. The house may be representing issues concerning a particular dilemma in your life, or it may be more general and comprehensive. Either way, if you pay attention to the details in this dream, you may learn a thing or two about yourself.
What room you were in is an important part of the dream because each room represents a different part of 'the self', and what area of emotion it pertains to.

Little Brother - The masculine part of yourself (psyche). Projection of those qualities you find in your brother onto someone else or yourself. May symbolize some aspect of your relationship with your real brother.  Because he is your little brother, it would suggest you envy his age, and the fact he has less reponsibility, and more 'play' time.

Unknown Baby - an unknown side of your 'self'. Babies represent vulnerability, or your need for love , also something that requires great care and attention. As your pure, innocent, true self (other than the ego)... It may represent some new development in your life.

Stranger in Black - would represent an unknown, 'darker' part of the self.
Black is the color of the subconscious, of sinking into the darkness, or mourning. Black is masculine; it is the color of night. Black stands for limitation, hidden things, despair, depression, things that are considered 'taboo', conservatism, old age, melancholy and sacrifice(the giving up of things to make you, or someone else happy), your shadow (an aspect of your personality that is hidden, unknown and/or repressed within your subconscious mind).

Walls - codes of behavior, belief systems, attitudes(conscious or subconscious) you live within or are 'protected' by, the boundaries of behavior or thoughts you keep within, are fearful of extending beyond, or are 'trapped' by..(which would represent barriers or restrictions).
Also your feelings of confidence that protect against anxiety or social 'knocks', fears that keep you limited in your activities, feelings or attitudes you keep people away with, ...the walls we put up between us to maintain privacy or to keep from being hurt, to maintain a role or status.

Threw the Baby againat a wall - suggests that one part of you is trying to 'do away' with a different, immature, side of you. Our violence is caused by emotions taking us over; and such emotional take-overs are the result of frustrated healthy desires.

Tying to hide the incident from parents. - represents a fear of facing some situation in your waking life, or trying to keep something from your family.
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Has someone (friend or authority figure) told you that you are 'immature, or that you are acting like a baby?
Are you having a hard time balancing your responsible life, with your fun life?
Did you do something for which you feel guilty, or don't want your parents to know?
Do you feel that you must be more sensible/responsible, and give up your 'childish' ways?
Are you angry with yourself for something you did, or didn't, do?

I hope this gives you something to go on, good luck!