Julius Caesar, not understanding the ironies..! Options

[hopelovebaby]

If any of you have read Julius Caesar, can you please help me explain some of these quotes and how they show irony, specifically situational irony?

1. Upon condition Publius shall not live, Who is your sister's son, Mark Antony. (4:1:6-7)
this is when antony and octavius are making a list of who to kill...so does something ironic and contradictory happen involving this? really confused...

2.This is a slight unmeritable man, Meet to be sent on errands: is it fit, The three-fold world divided, he should stand One of the three to share it? (4:1:14-17)
This is when Antony and octavius are discussing lepidus...once again i dont really see the irony.

3. Sheathe your dagger: Be angry when you will, it shall have scope; Do what you will, dishonor shall be humour. O Cassius, you are yoked with a lamb that carries anger as the flint bears fire; Who, much enforced, shows a hasty spark, and straight is cold again. (4:3:120-127)
-during brutus' and cassius' argument..

please please help if you know any possible explanations for these..
thank you so much =]]