Thanks for everyones approach / help , looks like i found the issue.
Its the irb interfaces which dont act "normally"( dont ping ) when all the referenced interfaces in a aggregated ethernet group are not physically connected.
For example i have 2 interfaces ge-0/0/8 and ge-0/0/9 under ae0 , both of them should be up ( connected physically ) even though you configure aggregated-ether-options to minimum-links 1.
Example config:
root@> show configuration interfaces ge-0/0/8 | display set
set interfaces ge-0/0/8 ether-options 802.3ad ae0
root@> show configuration interfaces ge-0/0/9 | display set
set interfaces ge-0/0/9 ether-options 802.3ad ae0
set interfaces ae0 aggregated-ether-options minimum-links 1
set interfaces ae0 aggregated-ether-options link-speed 1g
set interfaces ae0 aggregated-ether-options lacp passive
set interfaces ae0 aggregated-ether-options lacp periodic slow
set interfaces ae0 unit 0 family ethernet-switching interface-mode trunk
set interfaces ae0 unit 0 family ethernet-switching vlan members VLAN12
set interfaces ae0 unit 0 family ethernet-switching vlan members VLAN100
set interfaces ae0 unit 0 family ethernet-switching vlan members VLAN200
thanks