On holiday abroad last week visited DP's mothers place for a few days whilst there. On our last day there, DP's mother was looking after DP's cousins little girls (5 & 2) for the whole day as their parents were both working and their paternal GPs (the usual alternative caregivers in this case) were away on holiday that week.
DP's mother said she was about to take the kids for a walk whilst DP & I were setting up a BBQ in the garden. I popped back into the house to get some stuff from the freezer in the garage and I overheard DP's mother saying in a very flat tone of voice several times:
"your parents have abandoned you, you are all alone" 
Now my command of the said language is reasonably good in that I have spoken this language for 20 years, can hold a conversation and also understand nuance of tone of voice. I don't have children myself but I'm thinking that this is a pretty strange thing to say to children (regardless of language or culture). It did not appear to be part of a 'story' being told or part of a game or anything like that. Certainly in the case of these 2 children this is not true. Instinctively, my blood run cold.
Not the most elegant intervention I know, but the only thing I could think of at the time was to disrupt the flow of what appeared to be a really creepy monologue. So I walked into the area and asked DP's mother where I could find something for the BBQ. I then asked the children whether they liked sausages (yay!) and emphasised to them that the children's parents would be with us very SOON.
When I stepped into the room the children did not appear to be visibly upset or crying but were not happy or excited either. They had neutral expressions. DP mother did not give me much eye contact. I suggested that perhaps we could all go outside together. I asked the children if they would come and help us lay the table, make table place settings for everyone (including of course, their mum and dad).
I am still at a loss to understand what was going on here. This situation did not feel 'good' to me at all. AIBU should I have waited for something more concrete as evidence before clumsily stepping in?
I am not that familiar with the children's parents, only met them a few times. Without wanting to invoke the often discussed MiL/DiL dynamic (I don't really have a good relationship with DP mother at the best of times but put that down to personality preferences and try to remain civil) but this was really odd behaviour regardless IMO and because I am not that closely connected to the people involved unsure how to flag this up and with whom in a constructive way.
WWYD? 