Every coparcenary has interest in ancestral property. At any time even in the life time of father any coparcenary har right to demand his share in the property if father is agree because father is karta or manager of the ancestral property so his consent is necessary. If he refuses to give consent then you can file suit for partition,
in Jaswantlal Linabhai vs Nichhabhai Vallabhbhai And Ors. court has held that partition would be made according to the pleasure of the father.
State of Bombay v. Chhaganlal Gangaram Laver; supreme court has held that consent of karta should be necessary in a case for a suit for partition of joint family property.
Revanasiddappa & Anr vs Mallikarjun & Ors [2011] supreme court has held that the legitimate son acquires by birth any interest in his father's estate and he can therefore demand partition against his father during the father's lifetime.
your father is in ill health so your brother has opportunity to do any wrong , you should file suit for temporary injunction for protection of the property because you are living in USA, there after you can file suit for partition.