Danielle or Danni (maiden surname unknown, circa 40 BTS-6 BTS), the late mother of Reggie and Otto, who died when they were very little, was Raymundo's first wife. Her given name is a female variant of the Hebrew name "Daniel," which means "God is my judge."
Most of what we know about Danielle--including her appearance and her given name, which were unknown to us for a very long time--was learned in Island of the Menehune, very late in the series' run. That she had passed away some time before the series time frame had earlier been hinted at in Rocket X-mas, but in that episode she was not referred to by name.
From what little backstory we've been able to observe, we can surmise that Danni met Ray in Hawaii when she was living near or with the Makani family; Noelani was one of her best friends.
Although she only had one small line, the role of Danielle was read by Shayna Fox.
The causation and circumstance of Danielle Rocket's death still remains a mystery to the fans of the show. There are a few theories that have been thrown around:
~ She may have died in a freak surfing or scuba-diving accident as she had a passion for both activities. This theory seems to be the most popular of those discussed. One point, though, that may trump this theory is that Raymundo never seemed too wary of the ocean initially in the series as he never seemed to be excessively over-protective of Reggie and Otto when they were out in the water. Typically, when one's loved one dies in an accident of some kind, they would be emotionally traumatized by whatever caused said death to occur, especially if it is due to the force of nature like the ocean (this happened to Noelani after she and her friend were both in a bad tandem surfing accident). However, it is possible that Ray may have gotten over the fear that resulted in Danni's death (through therapy or with time) long before the time frame of the series.
~ She may have died of a terminal illness of some nature, such as cancer (a number of fanfics tend to subscribe to this possibility). Although it is a very generalized theory, illnesses are one of the most common ways to die. Usually when someone dies of a terminal illness, their family has time to prepare themselves emotionally for their passing. This theory could be very likely as many flashbacks in the series (referring to the ones where Otto and Reggie were very little, possibly just after Danni's death) show Raymundo in a positive state for someone who had just lost his wife. If she had died suddenly, right before these flashbacks, then Raymundo would more than likely be in a state of situational depression.
~ She may have died in a car accident. This theory is likely as it is a common way to die.
~ She may have been murdered. Although this theory is extremely far-fetched, it has been discussed in various forums and therefore cannot be ignored.
~ She may have simply died suddenly - Cause of death, unknown.
~She might have died due to either a rare disease or cancer at least.