HELP!

[RJLJ]

I need so advice I'm freaking out! This afternoon I caught my 4yr old daughter and 6yr
Old son with their pants down laying on one another. I instantly burst into tears and told them to
Get up stairs as they were in the back yard. I put them on their beds and asked them individually
What were they doing my son said he fell over and my daughter told me her brother told her to
Do it. I told them both that what they were doing was wrong and that they are brother and sister
An should never ever touch each other in that way! My partner and I are really blown away by this
We don't know what to do about it. Am I going to have to watch my kids play in the back yard together
Like a hawk from now on???? Is this going to happen again ??? How do I make them understand
That what they did was wrong ???? Please help the hole thing just keeps playin through my mind
Over and over again. Have I failed at being a mum for this to happen ??? My kids have never walked
In on my partner and I and we limit what they watch on tv. I'm lost ;-(

[adgal]

A friend of mine has calmly taught her children that no one should touch them in places their underwear covers.  You could sort of modify that and teach them that they shouldn't touch others in places that cover their underwear.  

I also agree with staying very calm and matter of fact about it.  Ask them each why they did this, and keep the conversation simple.  Answer questions openly and honestly, in child appropriate language (ie: they don't need all the details).  

[specialmom]

Could your 6 year old have seen something sexual either on tv or walking in on you and your partner??  I would also forbid it to be honest.  I have two boys and I'm really good at laying out the expectations such as DO NOT pull your pants down with any other children or lay on your sister again!!  They don't have to know that it made you think he was being sexual with her or whatever, just that it's a no no and that mom says that is not happening again.  
good luck

[AHP84]

This was probably nothing more than exploratory behavior between children of the opposite sex, which is pretty common. There are A LOT of posts about it in this forum if you scroll through and take a look.
Try not to be as upset and emotional with them about it, but rather, just keep calm and explain to them what is appropriate physical interaction/touching and what is not appropriate.
Telling them what they've done is "wrong" may scare and shame them, which you don't want them upset because they just don't understand the depth of what they've done. If you are absolutely confident there is no molestation going on with either of them with other family members, school, daycare, neighbors, etc. and you are confident they are not re-enacting or mimicking the behavior because you monitor what they see on TV and you know they haven't walked in on your partner and you, then I can assure you, they were just exploring inappropriately and had no idea it was inappropriate because no one has ever told them.
I do encourage you to scroll through this forum to see how common this is and how many other parents experience this with their children. There are a lot of good solutions and advice given throughout the years on this subject on this forum.