Ahh it's a trailer for a push-bike.burley coho xc
You could probably repair this with an solid aluminium insert bonded and bolted or a tube inside bonded and riveted.
Could be part of the reason why is has broken where is has.Quick google suggests the frame is 6061, so weldable, but doing so will soften the metal around it. May / may not matter, depending on the loads in the area.