In both cases, the jets were Max 8 models and in both cases, all aboard died.
Experts say the Boeing Company could be facing payouts in excess of US$1 billion if it can be proved that it had knowledge that the model had safety flaws.
Thirty individual lawsuits have now been filed against Boeing on behalf of families with many more expected, the Daily Telegraph reports.
"The bottom line is Boeing's exposure is much more substantial than in any other case that I've been a part of in my quarter-century of representing families'" in plane-crash cases, said Brian Alexander, a New York aviation lawyer for victims of the Ethiopian Airlines jet.
"You get into 'What did you know and when did you know it'."
The two disasters, with similar characteristics, led to the worldwide grounding of all Boeing 737 Max 8 models.
Both pilots desperately struggled to take control of the aeroplanes as they intermittently dived while reaching speeds of close to 965km/h.
Investigators have zeroed in on the malfunctioning Manoeuvering Characteristics Augmentation System, an automated safety feature designed to prevent a stall.
This month Dennis Muilenburg, the Boeing CEO acknowledged its automatic flight control system played a role in the two crashes.
"The full details of what happened in the two accidents will be issued by the government authorities in the final reports, but, with the release of the preliminary report of the Ethiopian Airlines Flight 302 accident investigation, it's apparent that in both flights the Manoeuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information."