Are Echinocactus and Nymphaea from the same family?
no
Nymphaea
Nymphaea is a genus of hardy and tender aquatic plants in the family Nymphaeaceae.
 The genus has a cosmopolitan distribution.
 Many species are cultivated as ornamental plants, and many cultivars have been bred.
 Some taxa occur as introduced species where they are not native, and some are weeds. Plants of the genus are known commonly as water lilies.
 The genus name is from the Greek νυμφαια, "nymphaia" and the Latin "nymphaea", which mean "water lily" and were inspired by the nymphs of Greek and Latin mythology.
Echinocactus
Echinocactus is a genus of cacti in the subfamily Cactoideae.
 The generic name derives from the Ancient Greek εχινος ("echinos"), meaning "spiny," and "cactus".
 It and "Ferocactus" are the two genera of barrel cactus.
 Members of the genus usually have heavy spination and relatively small flowers.
 The fruits are copiously woolly, and this is one major distinction between "Echinocactus" and "Ferocactus".
 Propagation is by seed.
Elachista nymphaea
Elachista nymphaea is a moth of the Elachistidae family.
 It is found in South Africa. Nelumbo nucifera
Nelumbo nucifera, also known as Indian lotus, sacred lotus, bean of India, Egyptian bean or simply lotus, is one of two extant species of aquatic plant in the family Nelumbonaceae.
 The Linnaean binomial "Nelumbo nucifera" (Gaertn.
) is the currently recognized name for this species, which has been classified under the former names, "Nelumbium speciosum" (Willd.
) and "Nymphaea nelumbo", among others.
 (These names are obsolete synonyms and should be avoided in current works.)
 This plant is an aquatic perennial.
 Under favorable circumstances its seeds may remain viable for many years, with the oldest recorded lotus germination being from that of seeds 1,300 years old recovered from a dry lakebed in northeastern China. Nymphaea alba
Nymphaea alba, also known as the European white water lily, white water rose or white nenuphar, is an aquatic flowering plant of the family Nymphaeaceae. Nymphaea odorata subsp. odorata
Nymphaea odorata" subsp.
 "odorata is a subspecies of "Nymphaea odorata" that is found in the United States.
 It has a very round leaf.
 The family is also called the "water-lily family". Nymphaea elegans
Nymphaea elegans, the tropical royalblue waterlily, is a species of aquatic plants in the family Nymphaeaceae.
 It is found in Louisiana, Florida and Texas, in the United States, in Oaxaca in Mexico and in Antioquia in Colombia. Nymphaeaceae
Nymphaeaceae is a family of flowering plants, commonly called water lilies.
 They live as rhizomatous aquatic herbs in temperate and tropical climates around the world.
 The family contains five genera with about 70 known species.
 Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on or emergent from the surface.
 The leaves are round, with a radial notch in "Nymphaea" and "Nuphar", but fully circular in "Victoria" and "Euryale". Nymphaea ondinea
Nymphaea ondinea is an flowering aquatic plant in the family Nymphaeaceae native to northwestern Australia.
 Originally classified in its own genus as "Ondinea purpurea", molecular studies have shown that it is morphologically aberrant species of "Nymphaea", to which it has been transferred.
 It grows from a corm-like rhizome and is found in ephemeral pools and rivers that are dry for a significant portion of the year.
 The rhizome survives the dry season in drying mud. Nymphoides
Nymphoides, or floatingheart, is a genus of aquatic flowering plants in the family Menyanthaceae.
 The genus name refers to their resemblance to the water lily "Nymphaea".
 "Nymphoides" are aquatic plants with submerged roots and floating leaves that hold the small flowers above the water surface.
 Flowers are sympetalous, most often divided into five lobes (petals).
 The petals are either yellow or white, and may be adorned with lateral wings or covered in small hairs.
 The inflorescence consists of either an umbellate cluster of flowers or a lax raceme, with internodes occurring between generally paired flowers.